While working on tracking down some tricky UI bugs in about:addons, I wondered
what it would look like to rewrite it using web technologies. I've been
meaning to learn React (which the Firefox devtools use), and it seems like a
good choice for this kind of application:

easy to create reusable components

XBL is used for this in the current about:addons, but this is a non-standard
Mozilla-specific technology that we want to move away from, along with XUL.

manage state transitions, undo, etc.

There is quite a bit of code in the current about:addons implementation
to deal with undoing various actions. React makes it pretty easy to track
this sort of thing through libraries like Redux.

Note that it's just a proof-of-concept and almost certainly buggy - the way
it's hooking into the existing sidebar in about:addons needs some work for
instance. I'm also a React newb so pretty sure I'm doing it wrong. Also,
I've only implemented #1 above so far, as of this writing.

I am finding React pretty easy to work with, and I suspect it'll take
far less code to write something equivalent to the current implementation.

Since publishing the Etherpad 2013 Meetup Videos a few weeks ago, the
main bit of feedback I have received is that they are too long/unedited,
and it's not trivial to pick out just the talks you want. Also transcripts
would be nice, for people too busy to watch ...

I have been working for a few months now on migrating Mozilla's Etherpad
install from the original Etherpad to Etherpad Lite. I got a chance to
work with a fair amount of people from the excellent Etherpad community
while working on things like adding "Team Site" support to Etherpad ...